Currently, electric power is the main stream of the available energy source in the world. In general, electric power is conveyed by power lines. Normally, the pylon that is used to set up the power lines to convey electric power is tens of meters in height. The workingman who works on the pylon is bound to expose himself to a high risk. Therefore, the workingman who works on the pylon is fastened with a safety belt to avoid an accident. However, the safety belt should not be too long, and a long safety belt is indicative of low security. Furthermore, in order to allow the workingman to shift around by the safety belt, one end of the safety belt must be tied to a safety device that can be slid with a human body. Typically, a safety device is telescoped into a safety rail designed for a specific purpose and can be slid in a forward direction only. If it is desirable to enable the safety device to be rapidly slid in a backward direction, brake action will occur immediately to stop the safety device from sliding and the safeguard function i.s achieved accordingly. The construction of conventional safety device for pylon is illustrated as follows.
FIG. 1 schematically shows a pylon under construction. It can be seen from FIG. 1 that a safety rail (2) is annexed to the main frame of the pylon (1). Rail switches (21) that are capable of turning the safety rail (2) with 90 degrees are respectively mounted at each intersections of the transverse braces (11), so as to connect with the safety rail on the transverse braces (11). After the safety device (3) is telescoped into the lower end of the safety rail (2), it will be shifted up along the safety rail through the connection with the safety belt together with the climbing of the workingman. If the safety device (3) is shifted to the location of the rail switch (21) and intends to move along the brace (11) horizontally, the rail switch (21) must be turned left or right with 90 degrees, and the safety device (3) may be transferred to the safety tail on the transverse bracing (11) to proceed with horizontal sliding.
FIG. 2 shows four side views of the conventional safety device for pylon, wherein FIG. 2-1 is a front view, FIG. 2-2 is a top view, FIG. 2-3 is a bottom view and FIG. 2-4 is a right-side view of the conventional safety device. FIG. 3 is a cross-sectional view taken along line Axe2x80x94A of FIG. 2-2. It can be seen from FIGS. 2 and 3 that the safety device is a frame-like structure including an upper frame and a lower frame that are adjustably connected together, wherein the upper frame is made of two parallel upper short steel pillars (4) that are fixedly connected together by a thick steel piece (41) and the lower frame is made of two parallel lower short steel pillars (5) that are fixedly connected together by a thick steel piece (51). The upper frame and the lower frame are adjustably connected through two parallel connecting rods (6a,6b) that are adjustably connected through transverse axles (61). Safety grooves (42,52) are respectively mounted on the inner side at the right end of the short steel pillars (4,5), and rollers (43, 53) are respectively mounted on the inside of the slit of the upper safety groove (42) and the outside of the slit of the lower safety groove (52). A connecting ring (33). is mounted on the left end of the lower frame where the safety belt (31) is connected thereto.
FIG. 4 shows a front view and a sectional view of the safety rail (2) according to the prior art, which is shown in the shape of an inverted letter xe2x80x9cHxe2x80x9d lying transversely and has a wider rail base (22) and a narrower rail shoulder (23). A number of perforations (221) are provided on appropriate locations on the rail base (22) for connecting with pylon (1). The safety groove (42,52) of the safety device (3) are telescoped into the rail shoulder (23) to proceed with sliding.
FIG. 5 schematically shows a safety device (3) being telescoped into a rail shoulder (23) to proceed with sliding according to the prior art. The width of the safety groove (42,52) is slightly larger than the thickness of the rail shoulder (23). While the safety belt (31) is pulled up with the workingman (32), it is pressed to contact with the rail shoulder (23) by two connection points within the rollers (43,53) due to leverage action. Therefore the safety device can be slid upwards smoothly without any resistance. However, in case of accident, the safety belt (31) that is fastened with human body will be pulled down, and here the connection points between the safety belt (31) and the rail shoulder (23) will be points (B,C) within the bevels of the two safety grooves (43,53). In this manner, forces will be generated so that a huge resistance is created between the safety device (3) and the rail shoulder (23) to stop the safety device (3) from falling. It is foreseeable that if the safety device is telescoped into the safety rail in an opposite direction, the safety device still can be pulled up due to the small pulling force, slow pulling speed and the little resistance generated between the points (B,C). In case of accident, the safety device will be pressed to contact with the rail shoulder (23) through rollers (43,53) without any resistance, and an immediate danger might occur. This point is indeed a drawback of the conventional safety device for pylon. Consequently, when the safety device for pylon is brought into use, the overseers have to pay enormous attentions to prevent the workingman from careless operation. When the workingman desires to shift to work on the transverse brace (11), the rail switch (21) has to turn right with 90 degrees (or turn left with 90 degrees) so that the safety device (3) can be slid rightward (or leftward) with the pull of the safety belt (31). At this moment the rail shoulder (23) is pressed to contact with rollers (43,53) without resistance. On the contrary, if the workingman shifts in an opposite direction, the points (B,C) are forced to be in contact. Though the pulling speed is slow and the pulling force is not large, the resistance is sufficient to make the safety device uneasy to be pulled. As a result, the workingman has to bend down to push the safety device manually. Nonetheless, it is difficult even impossible for the workingman to bend down frequently due to the environmental limitations of available working space on the brace. Such a difficulty in driving the safety device to slide in an opposite direction is another drawback of the conventional safety device for pylon. While the safety device is sliding in parallel (regardless of leftward sliding or rightward sliding), because the safety groove (42,52) are telescoped with two sides of the rail shoulder (23), it will not fall off from the safety rail at anytime.
The inventor has been engaged in the projects of pylon construction for years, and has been continuously making contributions to the improvements on the prior art to eliminate the drawbacks encountered by the conventional safety device for pylon. The present invention is attained by attaching an iron foil of great elasticity over the slit of the lower safety groove (52) to effectively prevent the safety device from reverse mounting, and mounting the oblique mobile blots on the steel pillars (5) of the lower frame of the safety device. When the safety device is shifting in parallel, the mobile bolts will automatically prop against the connecting rod to stop the upper frame and the lower frame of the safety device from parallel relative motion, such that the safety device will not meet with any resistance regardless of forward sliding or backward sliding. According to the present invention, the difficulty of the need to force the workingman to bend down frequently to push the safety device as the safety device is shifting in an opposite direction can be overcome, and the function of the safety device can be perfected.
The features and advantages of the present invention will become more apparent through the following descriptions with reference to the accompanying drawings, in which: